Grade 7 Science Review

Grade 7 Science Review Scientist Hypothesis Experiment Conclusion

Francisco Redi If flies could get to the He tested meat in 3 different jars. Proved that decaying meat meat and lay eggs, did not produce maggots. 1st jar- uncovered maggots would be DISPROVED theory of produced. - meat was exposed to the air spontaneous generation - flies were visible on the meat & jar

2nd jar- covered - meat in the jar is not exposed to the air - flies are visible on the cover of the jar but not inside the jar on the meat

3rd jar- covered with netting - the meat rotted - no maggots

John Needham Boiling broth would kill Conducted an experiment in which he placed a Claimed to have proved all living things. broth into a bottle, heated the bottle to kill spontaneous generation anything inside, then sealed it.

Days later, he reported the presence of life in the broth and announced that life had been created from nonlife.

Big mistake: He didn’t heat the broth long enough so both broths became contaminated.

Lazzaro Spallanzani Microbes come from Placed broth in two separate bottles, boiled broth Boiling did NOT damage the air. Boiling will kill in both bottles, then sealed one bottle and left the broth’s ability to support microorganisms. other open. Days later, the unsealed bottle life, growth depended on contained small living things. The sealed bottle the SEAL only. showed no signs of life. Disproved spontaneous 2 corrections he made: 1. boiled the broth and flask generation longer 2. sealed both flasks so no air could enter

Louis Pasteur Microbes come from He put broth into several S-shaped flasks. Each He reasoned that the cells of organisms on flask was boiled and placed at various locations. He contamination came from dust particles in the air; observed no life in the jar for one year. He then life-forms in the air. Definitions

Spontaneous generation The idea that living things can come from non-living things Controlled experiment Very structured, always contains the independent variable and dependent variable Biogenesis The theory that living things come from only other living things Who discovered the microscope? Anton van Leeuwenhoek

Theory A full explanation of an event in nature; subject to change Microorganism/Microbe Microscopic organism

Pasteurization Sterilizing milk Sterile Free from bacteria, totally clean

Other Concepts to Know

1. What are variables in an experiment? Factors to be tested

2. How many variables should an experiment test at one time? 1

3. What is a controlled experiment? Experimenter controls the variable to be tested; you control the IV

4. How a theory can be replaced or written – by interpreting existing data in new ways and including those views with new results

5. Identify the IV, DV & constant variables in an experiment.

6. Why did scientists in the 1800s use direct observation?